USING AN AMMONIA PROBE FOR PROCESS CONTROL TROUBLESHOOTING

An ammonia probe is a handy and underused tool for troubleshooting process control problems. Now that most plants are required to nitrify at least part of the year, many plants, even small ones, have ammonia probes. The probes themselves cost less than 400, and the selective ion meter (a fancy pH meter) used to measure the ammonia probe output may cost as little as 250.Why is an ammonia probe a good troubleshooting tool?Many plants are required to remove ammonia at least part of the year. The plant lab will have an ammonia probe and staff trained in its' use.Most plants remove ammonia by nitrification, a bacterial oxidation process.The nitrification reaction is relatively slow compared to BOD oxidation and, unlike BOD reduction, occurs at a steady rate throughout the secondary treatment process. This allows the operator to track the ammonia depletion with the ammonia probe.The nitrification reaction is sensitive to many common operating problems, such as lack of DO; recycle side streams and lack of detention time.The ammonia probe is easy to use and can measure ammonia in all types of samples, be they grab or composite, raw, final, mixed liquor, RAS or digester supernatant. The samples can be from the refrigerator or one grabbed only minutes ago.The five qualities mentioned above (and there may be more) allow the alert operator to detect many problems that may otherwise go unfound. Examples of problems that can be sniffed out by an ammonia probe are:Short-circuiting in an aeration tank.Poor influent or RAS distribution among multiple aeration tanksLack of DO in one tank, or in part of a tankRAS going septic in final settling tanksPoor air distribution among aeration tanksSupernatant or dewatering filtrate bleeding through the plant partially treated.Trickling filter media or snail problemsSolids decay in “tertiary” lagoonsThis paper will demonstrate how the ammonia probe can be used for troubleshooting and include real-world problems detected by ammonia probes.